Pumping problems😩

After 4 months of breastfeeding pumping has become very hard, I will pump for 30 minutes and only get 5 oz and my boobs still have lumps in them. I’ll have to wait 10 minutes to get the rest out. Before this I could easily pump 6/8 oz per pump. Any advice? My breasts are very uncomfortable that’s why I pump after feedings or when I’m not with him.